Shear stable,multiviscosity grade lubricating oils

ABSTRACT

COMPOUNDED LUBRICATING OILS HAVING IMPROVED PROPERTIES, INCLUDING VISCOSITY PROPERTIES, ARE OBTAINED BY THE USE OF HIGHER ALPHA-OLEFIN POLYMERS OF CONTROLLED MOLECULAR SIZE AND NARROW MOLECULAR WEIGHT DISTRIBUTION. A SHEAR STABLE, MULTIVISCOSITY GRADE LUBRICATING OIL IS PRODUCED BY ADDING THE ALPHA-OLEFIN POLYMER TO A LUBRICATING OIL.

March 5, 1974 w. J. HElLMAN ETAL SHEAR STABLE, MULTIVISCOSITY GRADELUBRICATION OILS Filed April 18, 1972 I I I I I I I A (polyhexeneadd/rive) SAE 40 grade Minimum B (pa/yacry/a/e add/five l l l I l //Vl/E N 701% 500 I000 /500 M/ L E5 8 THOMAS J. LYNCH United S tates PatentUS. Cl. 252-59 18 Claims ABSTRACT OF THE DISCLOSURE compoundedlubricating oils having improved properties, including viscosityproperties, are obtained by the use of higher alpha-olefin polymers ofcontrolled molecular size and narrow molecular weight distribution. Ashear stable, multiviscosity grade lubricating oil is produced by addingthe alpha-olefin polymer to a lubricating oil.

This application is a continuation-in-part of our patent applicationSer. No. 152,505, filed June 14, 1971, and now abandoned.

The present invention relates to novel, shear stable lubricating oilcompositions comprising an alpha-olefin polymer of controlled molecularsize and narrow molecular Weight distribution. More particularly, theinvention relates to a novel, shear stable lubricating oil compositioncontaining the alpha-olefin polymer of controlled molecular size andnarrow molecular weight distribution to significantly enhance the oilsviscosity grade as determined by established ASTM testing procedures.

In early days lubricating oils were selected for automobiles, trucks andsimilar vehicles on their ability to protect the engines componentsagainst wear and surface damage during operation. Kerosene addition tothe oil in winter was generally recommended to thin the oil for improvedcold weather starting, even though this degraded the lubricating qualityof the oil. Later when it was discovered that oils differed in theirchange in viscosity with changes in temperature, the existing oils wererated in this property, and selection of the more satisfactory oilscould be made from the existing oils for cold weather use. Thisviscosity-temperature relationship of an oil, expressed as its viscosityindex, was based on the viscosity temperature relationship of two knownoils which were selected as standards. However, since no reliable methodwas known for determining the 0 F. viscosity of an oil, viscosities wereobtained at substantially higher temperatures and its 0 F. viscosity wasdetermined by extrapolation. Sometime after this, high molecular weightorganic polymers were added to lubricating oils to decrease thetemperature effect on the viscosity, that is to increase the viscosityindex of the oils. It was later discovered that the viscosity index asderived from an ASTM D341 chart did not truly represent the cold weathercranking characteristics of the polymermodified oil since theviscosity-temperature curve of the polymer modified oil did notfaithfully respond to extrapolation. Thus it became known that viscosityindex is not a reliable indicator of the properties desired in apolymer-modified oil.

Originally automotive-type lubricating oils were classified by operatingtemperature viscosity in accordance with SAE specification and assigneda grade number such as SAE 20. This system has proven to be inadequatebe cause it does not provide an accurate indication of an unmodifiedoils cold weather starting characteristics. Furthermore. this system isnot a reliable in-use indicator of polymer-modified oils quality andcannot be used in conjunction with viscosity index, which, as indicated,is not a reliable index for these modified oils.

Todays automotive-type lubricating oils are to an increasing exentmarketed under multiviscosity grade designations, such as SAE 10W-30grade, SAE 10W-40 grade and the like in accordance with SAEclassification J300a. The first number in the grade designation is anindication of the cold temperature viscosity as determined at 0 F. bythe cold cranking simulator procedure (ASTM D2602-) and the secondnumber is an indication of the high temperature viscosity as determinedat 210 F. by a kinematic viscometer (ASTM D445). The high performanceoils have a wider spread in the numbers with SAE 51W-50 being thebroadest possible category in this SAE classification. Since adequatelyhigh viscosity is desired to protect the engines bearing componentsduring operation of the engine when heated to operating temperatures andadequately lo'w cold weather viscosity is desired in the same oil topermit easy winter starting, the multiviscosity grade designation, whichis the result of viscosity determinations on an oil at 0 F. and 210 F.,is a more reliable indicator of the most important physical propertiesof the lubricating oil.

As pointed out, special polymeric viscosity. modifiers have beenincorporated into petroleum based lubricating oils or suggested forincorporation in these oils for the intended purpose of improving theirinherent viscositytemperature characteristics for automotive uses, asmeasured by viscosity index. These materials include polyisobutylenes,polyacrylates, polyalkylstyrenes, polyalpha-olefins, ethylene-propylenecopolymers and the like. As indicated, multiviscosity grading and theintroduction of the cold cranking simulator procedure have nowsuperseded viscosity index grading of automotive-type lubricating oilsas being more reliable and meaningful, particularly with oils containingthese high molecular weight, organic polymer viscosity modifiers. When apolymer additive is used in conjunction with multiviscosity grading, itis desired by the use of the polymer additive to produce a lubricatingoil having the same 210 F. viscosity but a much lower 0 F. viscositythan a non-modified oil.

Although these polymeric materials can significantly improve theviscosity grade of a compounded oil prior to use, they are highlysusceptible to mechanical shear in the engine. Thus instability to shearresults in rapid in-use degradation of the 210 F. viscosity of thecompounded oil. In a relatively short time these viscositymodified oilsfail to meet the labeled SAE specifications. Thus, a 10W-40 grade oilcan quickly degrade to an SAE 10W-30 grade oil or even a 10W-20 gradeoil as the viscosity modifier is fragmented by the shearing forces inthe engine. Furthermore, the fragments resulting from the rupture of thepolymer tend to become chemically active, particularly acidic in nature,leading to engine corrosion such as valve corrosion. This corrosion isparticularly accentuated in the case of engines having positivecrankcase ventilation since the corrosive products are retained withinthe crankcase rather than being vented to the atmosphere. So general isthis in-use oil shear problem that essentially all commerciallyavailable viscosity-modified oils fail the labeled viscosity grade priorto the completion of the minimum miles of vehicle operation recommendedby the manufacturer before oil change.

Another problem with these high molecular weight polymer-modifiedlubricating oils is related to the non- Newtonian character of theseoils as a result of the polymer additives. These high molecular weightpolymers introduce non-Newtonian characteristics to the compounded oiland can cause test failure in the cold cranking simulator test (ASTMD2602 70) by causing the oil to leave the shear area and climb the rotorshaft of the cold cranking simulator. When this happens, it constitutesa test failure of the oil because it demonstrates the likelihood thatthe oil will leave the bearing surface in actual use. Thus, alubricating oil which is properly viscosity modified by means of a highmolecular weight polymeric additive must satisfy a number ofrequirements which are almost mutually exclusive, particularly for thehigher performance multiviscosity oils. That is, the polymer modifiedoil must (a) produce a useful 210 F. SAE viscosity, (b) it must notseveraly degrade under mechanical shear as determined by the sonic sheartest (ASTM D2603) or a -hour shear test in the L-38 test engine(MIL-b46152), or shear in an engine to an extent that the oil willreduce in grade (SAE J 300a) prior to the manufacturer-recommended milesbefore oil change, (c) it must permit easy engine starting as determinedby the cold cranking simulator test (ASTM D260270), and (d) it must notleave the shear area and climb the rotor shaft of the cold crankingsimulator during the test.

We have discovered that a high quality multiviscosity grade lubricatingoil that meets all of these requirements can be prepared by adding tothe oil a minor amount of a poly(l-olefin) of controlled molecularweight and molecular weight distribution. The resulting lubricatingcomposition is shear stable for extended periods of operation and willtherefore maintain its SAE multiviscosity grading. It exhibits goodviscosity characteristics at 210 F. and good 0 F. viscosity asdetermined by the cold cranking simulator test. Furthermore, it will notleave the shear area and climb the cold cranking simulator rotor shaft.This lubricating oil when fully compounded as a motor oil meets requiredlube oil specifications and maintains these specifications over a l0ngperiod of use.

The drawing is a graph comparing the viscosity stability of two oils inactual use under identical conditions. Both oils were compounded as SAEl0W-40 grade oils from the same base stock oil. Oil A contained 4.8percent of our novel polyhexene While oil B, commercially sold forautomotive use, contained 2.9 percent of a polyacrylate viscositymodifier. Both oils were identically tested in identical 1968 ChevroletV-8 automobiles, each having an engine displacement of 307 cubic inches.A magnetic tape was first made by driving a third automobile over acity-suburban route for a total of 2,000 miles to provide arepresentative balance of driving conditions. The test automobilescontaining oil A and oil B, respectively, were placed side-by-side ondynamometers in a temperature controlled test laboratory and theiroperation was controlled by the tape. A full simulation of the operationof the third automobile was effected in each test automobile includinglow speed and high speed driving, acceleration, braking, stopping,starting, hill climbing, ambient temperature, and the like, for theequivalent 2,000 miles. Periodic studies of the test oils, includingviscosity, and engines were made. The graph shows that the 210 F.viscosity of oil A, the novel polyhexene modified oil, decreases about2.5 SUS after 1,000 miles of operation and then increases the remaining1,000 miles. On the other hand the 210 F. viscosity of oil B, thecommercial polyacrylate-modified oil decreases continuously, about threeSUS the first 500 miles and about six SUS for the full 2,000 miles. Thistest fully demonstrates the remarkable stability of our novel poly(l-vhexene) modified oil in actual engine use.

The poly(l-olefin) which we add to the lubricating oil can be thepolymer of any single straight or branchedchain alpha-olefin monomerfrom l-pentene to l-dodecene and preferably from l-pentene to l-decene.In addition, copolymers of any of the above alpha-olefins can be used aswell as copolymers of the above with propylene, isobutene and l-butene.The polymers formed from monomers larger than about l-dodecene and thosesmaller than about l-pentene tend to crystallize out of oil at lowtemperatures and this property interferes with their utilization. Forexample, three and four carbon polyoelfins are solids at lowtemperatures and cannot be used unless they are copolymerized with atleast about 20 mol percent and preferably at least about 50 mol percentof a higher alpha-olefin such as l-hexene. The most preferred monomer isl-hexene either polymerized alone or copolymerized with one or more ofl-butene, l-octene or l-decene. The useful branched chain monomersinclude 4-methyl-l-pentene. The alpha-olefins of odd carbon num berswithin the defined range are usable but are much less plentiful than theeven-numbered carbon olefins.

The poly(l-olefins) can be described as a mixture of long chainmolecules formed with a series of repeating units having the structuralformula in which. m is the carbon number of the starting alphaolefin andn is the number of repeating units in an individual molecule. Whenl-hexene is the monomer, m is six. When l-deceue is the monomer, m isten, etc. When a mixture of alpha-olefins is used, such as l-hexene andl-decene, the different alpha-olefins join together in the chainrandomly in essentially the same molar ratio that each alpha-olefinoccurs in the initial mixture. The polymer chains terminate withhydrogen or with a double bond.

The high quality, shear stable, multiviscosity grade lubricating oil isobtained under our invention when the molecular weight and the molecularweight distribution of the alpha-olefin polymer additive are controlledwithin critical limits. High molecular weight organic polymers generallycontain a mixture of molecules occurring over a vast range in molecularweight. This includes polymers of alpha-olefins. A high molecular weightpolymer can be defined in terms of the Weights and distribution of themolecules forming it by means of its weight average molecular Weight Mits number average molecular weight M and the distribution factor M /MValues for these concepts, as represented by the specified symbols,provide a good indicator of the distribution of the molecules andmolecular weights in the polymer and, as stated, are the basis for thedefinition of the useful alpha-olefin polymer additives describedherein.

The classification SAE J 300a specifies viscosity numbers formultiviscosity oils (together with the viscosity ranges defining eachnumber) in the order listed as follows: 5W, 10W, 20W, 20, 30, 40 and 50.The viscosity numbers with the letter W are based upon the 0 F.viscosities and the numbers Without a W are based upon the 210 F.viscosity. A multiviscosity numbered oil is one whose 0 F. and 210 F.viscosities fall within one of the prescribed viscosity ranges for both0 F. and 210 F. Multiviscosity numbered oils having a difference inviscosity numbers as set out in the above list of less than three areeither not desired or are readily obtainable and therefore do notrequire high molecular weight polymer additives. These oils are SAE10W-20, 20W-20 and 20W-30 oils.

However, the novel poly( l-olefins) described herein are particularlyuseful for producing high quality, shearstable, multiviscosity numberedoils having a difference in the listed viscosity numbers of three ormore and more particularly four or more. The greater the difference inthe SAE multiviscosity numbers, the more difficult it is to compound theoil. Therefore, the greater the difference in the SAE multiviscositynumbers the more beneficial as Well as necessary are thesepoly(l-olefins) for producing a satisfactory oil that can pass lube oilspecifications. Those oils having a difference of three in their SAE.multiviscosity numbers are SAE 5W-20, 10W-30 andl 2'0W-40 oils; thosewith a difference of four in their mlfll tlitiscqsiity numbers are SAE5W-30, W-40 and W-50 oils; those with a difference of five in theirmultiviscosity numbers are SAE 5W-40 and 10W-50 oils, leaving SAE SW--50 as the only multiviscosity numbered oil having a difference of six inits multiviscosity numbers.

We have discovered that the high quality, shear stable, multiviscositygrade lubricating oil having a difference of at least three in the SAEmultiviscosity number is obtained with poly(l-hexene) when its weightaverage molecular weight M is between about 50,000 and about 1,000,000;its number average molecular weight M is between about 4,000 and about1,000,000, and its distribution factor M /M is between 1 and about 12with M /M being between 1 and about 12 when M is about 50,000 and beingbetween 1 and about 2 when M is about 1,000,000 with the upper range ofthe distribution factor proportionately increasing from about 2 to about12 as the M decreases from about 1,000,000 to about 50,000.

When the novel poly(I-hexene) is used to produce a shear stable,multiviscosity numbered lubricating oil having a difference of at leastfour numbers in the SAE multiviscosity number, the weight averagemolecular weight M is between about 100,000 and about 1,000,000, thenumber average molecular weight M is between about 12,000 and about1,000,000, and the distribution factor M /M is between 1 and about 9with M /M being between 1 and about 9 when M is about 100,000 andbetween about 1 and 2 when M is about 1,000,000 with the upper range ofthe distribution factor M /M proportionately increasing from about 2 toabout 9 as the weight average molecular weight M decreases from about1,000,000 to about 100,000.

When the novel poly(l-hexene) is used to produce a shear stable,multiviscosity numbered lubricating oil having a difference of at leastfive numbers in its SAE multiviscosity number, the weight averagemolecular weight M is between about 150,000 and about 1,000,000, thenumber average molecular weight M is between about 35,000 and about1,000,000 and the distribution factor M /M is between 1 and about 6 withM /M being between 1 and about 6 when M is about 150,000 and betweenabout 1 and 2 when M is about 1,000,000 with the upper range of thedistribution factor M /M, proportionately increasing from about 2 toabout 6 a the weight average molecular weight M decreases from about1,000,000 to about 150,000.

When the novel poly(l-hexene) is used to produce a shear stable,multiviscosity numbered lubricating oil having a difference of sixnumbers in its SAE multiviscosity number, the weight average molecularweight M is between about 200,000 and about 1,000,000, the numberaverage molecular weight M is between about 90,000 and about 1,000,000and the distribution factor M /M is between 1 and about 3 with M /Mbeing between 1 and about 3 when M is about 200,000 and between 1 andabout 1.5 when M is about 1,000,000 with the upper range of thedistribution factor M /M proportionately increasing from about 1.5 toabout 3 as the weight average molecular weight M decreases from about1,000,000 to about 200,000.

The lower the Weight average molecular weight M of a poly(l-olefin) themore difficult it is to produce a multiviscosity numbered lubricatingoil having a difference of at least three numbers in its SAEmultiviscosity number, since the 0 F. viscosity value tends to be. toohigh to pass the desired grade. However, the lower the weight averagemolecular weight of the polymer the more shear stable it becomes. On theother hand the higher the weight average molecular weight M the morelikely it is that the lubricating oil will leave the shear area andclimb the shaft of the cold cranking simulator to fail the test.Furthermore, the lower the distribution factor at the same weightaverage molecular weight, the less increase in 0 F. viscosity for agiven amount added to a specific base oil to get a desired 210 F.viscosity.

The critical distribution of molecular weights as indicated by M and Mdepends on the specific monomer used. Thus, the critical ranges for Mand M varies directly with the ratio of the molecular weights of thealphaolefin monomers or the average molecular weight of the alpha-olefinmonomer mixtures. However, the range of critical distribution factorsdoes not change regardless of the monomer or mixture of monomers fromwhich they are made. For example, the molecular weight of l-decene is5/3 times the molecular weight of l-hexene. Thus the critical ranges ofweight average molecular weight and number average molecular weight forpoly(l-decene) is 5/3 that of poly(l-hexene). These ranges arecalculated for any poly( l-olefin) from the ranges specified above forpoly(l-hexene) using the molecular weight ratio of the monomers. In likemanner the critical distribution of molecular weights as indicated by Mand M for a poly- (l-olefin) made from a mixture of monomers containingmol percent l-hexene and 20 mol percent l-decene is about 95.2/84 timesthe equivalent values for poly(lhexene), since the average molecularweight of the mixture is about 95.2.

We have discovered, as the above values indicate, that the desirableproperties in the poly(l-olefin) are directly related to the number ofrepeating units in the poly(lolefin) regardless of the starting monomeror mixture that is used. Thus the molecular weight at the weight averagemolecular weight can be expressed by the equation M =n M where nrepresents the calculated number of repeating units n at the weightaverage molecular weight and M is the molecular weight of the monomer,and the molecular weight at the number average molecular weight can beexpressed by the equation M =n M where n represents the calculatednumber of repeating units n at the number average molecular weight. Theeffect of the small terminal groups in these molecules is excluded fromthe equations since their effect is inconsequential in view of the largesize of the molecules. Furthermore,

and n -=M /M:M /M where M represents the average molecular weight in amixture of alpha-olefin monomers. Thus, as stated, the ranges for 11,,and n are found to be constants regardless of the alpha-olefin monomeror mixture of alpha-olefin monomers that is used. From these equationsit is apparent that M /M =n /n verifying that the critical distributionfactor herein is independent of the molecular weight of the startingalpha-olefins.

The addition to a base stock lubricating oil of only a minor amount ofthe poly(l-olefin) having weight and number average molecular weights, Mand M and a molecular weight distribution M /M within the limitsspecified herein, is required to produce a multiviscosity graded oilhaving a diiference of at least three in the SAE multiviscosity number.For example, we have determined that the addition of a poly(l-hexene) asdefined herein will produce desirable results in the lubricating oilwhen it constitutes from about 0.5 to about 10 weight percent of theoil, preferably between about 1.0 and about 6.0 percent and mostpreferably about 1.0 to about 3.5 percent of the oil. In general, thehigher the weight average molecular weight M for a series of polymersmade from the same monomer at equivalent distribution factors, the lesspolymer required for a given oil to produce equivalent results. Also,the lower the viscosity of the base oil, the more polymer additive thatis necessary to produce the desired viscosity grade.

Furthermore, we have discovered that the eifect of the poly(l-olefin)upon the lubricating oil is a function of the number of repeating unitsin the polymer and is therefore a function of the molecular weight ofthe monomer or average molecular weight of the mixture of monomers fromwhich the polymer was made. Thus, we have determined that the weightpercent of any polymer to be used in a lubricating oil can be determinedby reference to the amounts of poly(l-hexene) used or required. Theamount of the poly( l-olefin) to be used is obtained by multiplying thepercent of poly(l-hexene) used or required by the ratio of the molecularweight of the alpha-olefin from which the poly(l-olefin) is made and themolecular weight of l-hexene, M/ M or M /M wherein M is the molecularweight of the alpha-olefin, -M is the average molecular weight of themixture of alpha-olefins and M is the molecular weight of l-hexene.Thus, if four percent of a particular poly(l-hexene) is required toproduce a desired result in a lubricating oil then four percent times (M/M or 6.67 percent of a poly(l-decene) having equivalent properties isrequired to produce a similar result. Since the amount of apoly(l-olefin) required to produce a given effect increases with anincrease in the molecular weight of the starting alpha-olefin, otherthings being equal, it is generally preferred to use a poly(lolefin)prepared from a lower alpha-olefin such as l-hexene.

A fully compounded lubricating oil as prepared for automotive usecontains many additives that must be used to meet various specificationsor to overcome various deficiencies. One advantage of the poly(l olefin)additive described herein for improvement of the viscositycharacteristics is that it is fully compatible with and does notinterfere with or detract from the functioning of other additives. Otheradditives which are added to the oils are preferably those which havedemonstrated their effect by actual use and include pour pointdepressants, antioxidants, blooming agents, detergents, dis persants,rust inhibitors, anti-wear agents, anti-foam agents, extreme pressureagents, corrosion inhibitors, sludge inhibitors, metal deactivators,anti-scufiing agents, and the like. These additives are selected andused to meet desired specifications or overcome deficiencies in the baseoil with respect to the intended use in accordance with procedures whichare conventional and well known to those in the field of compoundinglubricating oils.

The poly(l-olefins) of this invention which have the critical ranges ofweight average molecular weights M number of average molecular weights Mand molecular weight distribution M /M are preferably made, bycatalyzing the alpha-olefin or mixture of alpha-olefins using aZiegler-Natta type catalyst. Either continuous, semicontinuous in whichonly the alpha-olefin is added during reaction, or batch polymerizationcan be used, provided that all conditions and proportions of chemicalspecies present in the reaction mixture are propertly correlated witheach other to obtain the necessary molecular weights and distribution.Any Ziegler-Natta type catalyst can be used which is useful for thepolymerization of propylene. Particularly useful are titanium andvanadium salts, primarily the chlorides, in conjunction with aluminumalkyls and alkyl chlorides. We have found that purple titaniumtrichloride together with aluminum triethyl constitutes an excellentcatalyst. A catalyst containing from about one to about ten gram atomsof aluminum per gram atom of titanium is useful with a ratio of about1.8 to about three being preferred. The reaction is suitably carried outusing about 300 to about 6,000 grams of olefin per gram of catalyst andpreferably from about 1,500 to about 3,000 grams of olefin per gram ofcatalyst.

Hydrogen or another suitable molecular chain length modifier such aszinc chloride, dialkyl zinc such as diethyl zinc and the like helps todirect the reaction to the desired molecular Weight distribution. Thepartial pressure of hydrogen can broadly be between about 0.1 and about150 psi. and preferably between about 0.5 and about 25 for a continuouspolymerization and between about 0.5 and about 10 for a semi-continuousor batch reaction. The temperature at which the polymerization reactionis conducted can suitably be between about 100 F. and

8 about 250 F. and preferably between about 220 F. and about 250 F.

A suitable solvent for the reaction mixture is desirable since theresulting polymer is highly viscous and can be substantiallynon-flowable at room temperature. Suitable solvents include hydrocarbonsolvents such as butane, pentane, hexane, heptane, and the like,naphtha, gasoline fractions, kerosene, gas oil fractions, furnace oilfractions, light lubricating oils, heavy lubricating oils and the like.Organic hydrocarbon solvents such as benzene, toluene, the xylenes andthe like and chlorinated hydrocarbon solvents are less preferred. Themost preferred solvents are those light solvents which can be easilydistilled from the product polymer or mineral oils which can beincorporated in the finished oil together with the polymer. Since asolvent is not necessary, it can be used in amounts from zero percent toabout 75 percent, and when used it is preferably used in an amount ofabout 25 to about 50 percent.

Variables which affect the Weight average moleculer weight, the numberaverage molecular weight or the molecular weight distribution includethe reaction temperature, the partial pressure of hydrogen, the amountof catalyst, the titanium/aluminum ratio in the catalyst, the titaniumcompound used, the olefin to catalyst ratio, the olefin concentrationand the like. Furthermore, it is essential that certain deleteriousimpurities, particularly those containing oxygen such as air, water andthe like be excluded from the reactor if the poly(l-olefins) of thespecified characteristics are to be obtained. Even minute amounts ofoxygen significantly broaden the distribution. In contrast with thisrequirement, it is well known that it is advantageous to add minuteamounts of oxygen or oxygen containing compound to the alpha-olefinpolymerization reaction in order to substantially increase the yield ofproduct per amount of catalyst used as well as the isotacticity.Therefore, minute amounts of oxygen are generally beneficial inalpha-olefin polymerizations.

The polymer made by the Ziegler-Natta type catalyst containssubstantially completely a head-to-tail alignment of the repeating unitsin the molecules forming the polymer. We have found that the purpletitanium trichloride makes an isotactic poly(l-olefin) which is superiorto the atactic poly(l-olefin) made by the use of brown titaniumtrichloride as a lubricating oil additive hereunder. However, anysuitable Ziegler-Natta catalyst system can be used provided that allconditions and variables are proper 1y correlated to produce thenecessary molecular weights and distribution.

We have found that the poly(l-olefin) having the critical relationshipof molecular weights, M and M and molecular weight distribution M /M isparticularly useful for improving the viscosity characteristics ofmineral lubricating oils. The expressions weight average molecularweight M number average molecular weight M and molecular weightdistribution M /M are well known and useful in the field of highmolecular weight polymers. A useful description of these expressions isfound in Chapter 1 of The Structure of Polymers by M. L. Miller,Reinhold Publishing Corporation (1966). In our Work these expressionswere determined by gel permeation chromatography using an instrumentthat was calibrated using known standard poly(l-hexene) fractions.

The following examples are set out to illustrate our invention and toprovide a better understanding of its details and advantages. In theexamples, except Where specifically indicated, all reactants, solventsand catalysts were of ultra-high purity for the reaction. For example,the heptane solvent was purified to about 10 parts per billion oxygen.

EXAMPLE 1 A high molecular weight polymer of l-hexene was made in a 0.5liter stirred reactor by a continuous process. 1- hexene was introducedinto the reactor at the .rate of 900 ml. per hour. A catalyst wasprepared by reacting a 1.3 weight percent solution of triethyl aluminumin heptane with a 0.17 weight percent solution of (TiCl -AlCl (obtainedfrom Stauffer Chemical Company and designated as titanium trichlorideAA-purple crystalline) in heptane in a stirred reactor at 100 F. under10 p.s.i.g. of nitrogen. The catalyst stream contained a molar ratio ofaluminum triethyl to titanium trichloride, TiCl of two to one and wasintroduced into the polymerization reactor at the rate of 900 ml. perhour. The reactor was maintained at 240 F. and was pressured withhydrogen to a pressure of 52 p.s.i.g. A product stream was continuouslyremoved from the reactor at the rate of 1,500 ml. per hour whichprovided an average residence time for the 1- hexene in the reactor of20 minutes.

The stream that was removed from the reactor was a mixture ofpoly(l-hexene), unreacted l-hexene, heptane and trace amounts of thecatalyst. The catalyst was killed by mixing a 10 percent aqueous sodiumhydroxide solution with the hydrocarbon stream. The water solution wasseparated from the hydrocarbon solution by decantation. The hydrocarbonsolution was then water-washed, dried and filtered. The hydrocarbonsolution was next mixed with sufficient light neutral oil having a 210F. viscosity of 4.15 centistokes (cs.) to form a 50 weight percentsolution of poly(l-hexene) in the oil after the l-hexene and heptanewere stripped off to a flash point of 380 F.

The poly(l-hexene) was recovered in a 70 percent yield based on thel-hexene fed to the reactor. It was determined to possess a weightaverage molecular weight M of 92,000, a number average molecular weightof 11,000 and a molecular weight distribution of 8.5.

This polyhexene-oil mixture, two different lube oil base stocks and anadditive mixture were mixed together to form a compounded oil containing4.9 weight percent polyhexene, 39.9 percent light neutral oil having a210 F. viscosity of 4.15 cs., 45.9 percent of a medium neutral oilhaving a 210 F. viscosity of 5.32 cs. and 9.3 percent of the additivemixture. These additives were commercially used materials and were addedto provide a fully compounded lube oil suitable for actual use so thatthe testing and evaluation would be fully meaningful. The mixturecontained a dispersant, a detergent, a pour point depressant and ananti-foam agent.

The viscosity index of the light neutral oil was 98 and that of themedium neutral oil was 116. The 210 F. viscosity of the resulting fullycompounded oil-polymer mixture was 14.3 cs. which classifies it as anSAE 40 grade oil. Its 100 F. viscosity was 94.0 cs. which gave it aviscosity index of 170 by ASTM D34-43. The oil-polymer mixture was foundto have a F. viscosity of 2,300 centipoises (cp.) by ASTM D2602-70 whichclassifies it as an SAE l0W-40 grade oil.

The pour point was found to be -25 F. The shear stability of theoil-polymer mixture was determined by ASTM D2603. It was found that the210 F. viscosity was reduced to 13.20 cs. after minutes representing aloss of 1.1 cs. An equivalent oil containing 2.9 percent of acommercially used polyacrylate viscosity modifier had a 2.4 cs.viscosity loss from 13.92 cs. to 11.54 cs. in the same test.

EXAMPLE 2 Another poly( l-hexene) material was made in the same manneras used in Example 1. A l-hexene-heptane solution was introduced intothe 0.5 liter reactor at the rate of 800 ml. per hour based on l-hexeneand 400 ml. per hour based on heptane. A catalyst was prepared byreacting a 2.7 weight percent solution of triethyl aluminum in heptanewith a 0.5 weight percent slurry of -(TiCl -AlC 'in heptane in a stirredreactor at 120 F. under 8 p.s.i.g. of hydrogen. The catalyst streamcontained a molar ratio of aluminum triethyl to titanium trichloride,TiCl of two to one and was introduced into the polymerization reactor atthe rate of 1,200 ml. per hour. The reactor was 10 maintained at 240 F.and was pressured with hydrogen to a pressure of 40 p.s.i.g. A productstream was continuously removed from the reactor at the rate of 2,000ml. per hour which provided an average residence timein the reactor forthe l-hexene of 15 minutes.

The product was recovered in percent yield as a 40 percent solution ofthe poly(l-hexene) in the same light neutral oil as used in Example 1.It was determined to have a weight average molecular weight M of 120,000and the distribution factor was determined to be 7.3 from its sonicshear and 0 F. viscosity data.

This po1y(l-hexene)-oil mixture was mixed with the same light neutraland medium neutral base stocks as used in Example 1 as well as anadditive mixture. The fully compounded lube oil mixture contained 4.8weight percent of the poly(l-hexene), 37.2 percent of a light neutraloil having a 210 F. viscosity of 4.15 cs., 50.1 percent of a mediumneutral oil having a 210 F. viscosity of 5.32 cs. and 7.9 percent of theadditive mixture. This oil was compared in a road simulator test with anoil in actual commercial use containing a polyacrylate polymer forviscosity modification. This polyacrylate compounded lube oil contained7.8 weight percent of a concentrate containing 37.2 weight percent ofthe polyacrylate in an oil solution, 15.0 percent of a medium neutraloil having a 210 F. viscosity of 7.0 cs., 69.8 percent of a mediumneutral oil having a 210 F. viscosity of 5 .32 cs. and 7.4 percent of asimilar additive mixture.

Each oil was placed in one of two identical 1968 Chevrolet V-8automobiles. They were operated side-by-side on dynamometers in a testlaboratory and were controlled by a magnetic tape which was made by acar driven for 2,000 miles over a balanced city-suburban route. Thistest represented identical usage for 2,000 miles equally simulatingacceleration, braking, various constant speeds, air temperature, hillclimbing and the like. The oils were tested at intervals. Table I liststhe comparative viscosity data of these two oils that resulted from thisengine shear test:

TABLE I Miles Poly(1-hexene): Viscosity at 100 F. SUS 432 451 431 425463 210 F. SUS l 74.9 75.4 73.4 72.3 75.2 Polyacrylate: Viscosity at-100 F. SUS 389 368 368 359 360 210 F. SUS b 73.0 70.4 70.4 68.1 67.1

A high molecular weight poly(l-hexene) was made in a 30 gallon stirredreactor. While a hydrogen blanket was maintained in the reactor, 65pounds of a light neutral oil, one pound of a six weight percentsolution of triethyl aluminum in a 22 to 28 carbon alpha-olefin wax and0.05 pound of (TiCl -AlCl were added to the reactor. After the reactorwas heated to 2400 F. under a constant blanket of hydrogen at a pressureof 19 p.s.i.g., l-hexene was pumped into the reactor at 1.35 pounds perminute for 75 minutes. The mixture was stirred at the same temperatureand hydrogen pressure for an additional hour. The contents were removedfrom the reactor and quenched with 20 percent sodium hydroxide, washed,dried, filtered and stripped to a 380 F. fiash point. The yield ofpoly(l-hexene) was percent based on 1-hexene charged to the reactor. Theproduct was 38.6 percent poly(l-hexene) in the light neutral oil havinga viscosity of 39.9 SUS at 210 F. It was used to make a series of fullyformulated motor oils as set out in Table II.

TABLE II Poly(1- Base oil hexene), Finished Shear 210 w oil 210 loss BCCS, SAE grade SUS percent F., SUS SUS cp. after shear 1.7 76 6 2,150low-40 fiLgss on shear after 10 minute exposure in sonic shear test,ASTM 2 0 b Cold cranking simulator.

EXAMPLE 4 A 50 gallon glass-lined reactor was charged with 178.4 poundsof n-heptane, then sealed, evacuated and purged with nitrogen. Thereactor was kept sealed and 542.3

grams of (TiCl -AlCl was introduced followed by 20 oil. The viscosityindex Was calculated as 137 by ASTM D567 and 166 by ASTM D2270. After 10minutes in the ultrasonic oscillator (ASTM D2603) the viscosity loss was0.86 centistoke at 210 F. and 6.7 centistokes at 100 F. giving aviscosity index loss of 1 and 3 by D567 and D2270, respectively. The oilremained an SA'E 10W-40 grade oil after the sonic shear test.

EXAMPLES 5 TO 28 A series of l-hexene polymers were made by the generalprocedures of Examples 1 or 3 but with variations in the conditionsunder which the polymer was made in order to obtain polymers withdifferent average molecular weights and molecular weight distributionsso that they could be evaluated as viscosity modifiers in mineral oilformulations. The results of these evaluations are set forth in TableIII. The 210 F. viscosities in Table III were determined according toASTM D445 and the 0 F. viscosities by the cold cranking simulator (CCS)in accordance with ASTM D2602-70. The loss on shear was determined byASTM D2603. Where it is indicated that the oil failed the CCS viscositytest, failure resulted from the formulated oil leaving the test sectionand climbing the rotor shaft of the cold cranking simulator. Those 5polymers made with a distribution factor of 1.5 included a fractionationstep.

TABLE III Polymer, Base oil, Oil mix- SAE wt. cs. at ture cs. Shear 008,Example grade percent 0 F. at 210 F. loss, cs. cp. Mw Mn Mw/ n 1. 5 3. 25. 7 0. 75 550 190, 000 23, 000 8. 3 3. 0 5. 3 10. 6 0. 70 2, 100 00010, 000 3. 7 3. 0 5. 3 10. 1 0. 50 2, 250 76, 000 9, 000 8. 5 3. 0 4.10. 4 0. 80 1,350 155, 000 18, 500 8. 4 2. 5 4. 15 11. 2 1. 60 1, 410190, 000 23, 000 8. 3 4. 0 4. 15 11. 3 0. 60 1, 675 61, 000 17, 000 3. 62. 7 6. 00 14. 1 1. 15 4, 360 155, 000 18,500 8. 4 2. 2 6. 00 14. 2 1.4, 200 190, 000 23, 000 8. 3 3. 3 3. 2 11.0 1. 4 840 190, 000 23, 000 8.3 1. 5 5. 3 16. 3 2. l 2, 000 610, 000 170, 000 3. 6 2. 5 5. 3 15. 0 2.3 Failed 260, 000 19, 000 13. 7 5. 0 5. 3 13. 4 0. 6 2, 570 76, 000 9,000 8. 5 7. 0 4. 2 14. 2 0. 6 2, 245 76, 000 9, 000 8. 5 4. 6 4. 214.0 1. 1 1, 775 155, 000 18, 500 8. 4 3. 9 5. 3 14. 2 1. 2 2, 250 155,000 18,500 8. 4 3. 8 4. 2 14. 9 2. 0 1, 720 190, 000 23, 000 8. 3 2. 85. 3 15. I 1. 7 2, 170 190, 000 23, 000 8. 3 4. 0 6. 0 18. 1 1. 3 5, 750155, 000 18, 500 8. 4 3. 4 6. 0 18. 2 1. 4 5, 660 190, 000 23, 000 8. 34. 5 3. 2 14. 7 1. 8 1, 065 190, 000 23, 000 8. 3 4. 1 5. 0 18. 5 1. 92, 300 190, 000 23, 000 8. 3 4.0 5. 3 18.3 1. 7 2, 400 175, 000 18,0009. 7 2. 0 5. a 21. 5 2. 1 2, 160 610, 000 170, 000 a. 6 4. 0 4. 2 24.0 1. 7 2, 125 270, 000 75, 000 3. 6

l-decene was charged to the reactor and the temperature was raised to146 F. at 10 p.s.i.g. of hydrogen.

After standing for one hour at these conditions, one liter of percentaqueous sodium hydroxide was added to quench the catalyst. A portion ofthe hydrocarbon phase was separated from the aqueous phase, washed,dried and diluted with 7.35 pounds of light neutral oil having a 210 F.viscosity of 4.15 cs. and stripped of volatiles. The resultingconcentrate contained 55 weight percent of the poly( l-decene) andpercent of the light neutral oil. The poly(l-decene) was determined tohave a weight average molecular weight M of 270,000, a number averagemolecular weight M of 37,000, and a molecular weight distribution M /Mof 7.3.

A compounded oil was formulated which contained 9.5 weight percent ofthis concentrate (about 5.23 percent polydecene), 82.8 percent of amedium neutral base oil having a 210 F. viscosity of 5.32 centistokesand about 7.7 percent of a dispersant, pour depressant and antifoamadditive mixture. This oil possessed a 210 F. viscosity of 13.82centistokes, a 100 F. viscosity of 92.2 centistokes and a 0 F. viscosityof 2,050 centipoises by the cold cranking simulator. This oil was an SAE10W-40 grade EXAMPLES 29 AND 30' In Table IV the results of adding apolyisobutylene, which is commercially used for modifying the viscositycharacteristics of oils, to a light neutral oil having a 210 F.viscosity of 4.15 cs. are set out.

TABLE IV Viscosity Amoun wt. 210 F., CCS, Loss on Example Additivepercent cs. op. shear 29 Po1yisobutylene- 8.5 13.84 Failed-- 0.7 30 d09.3 15.03 do.. 0.8

We claim:

1. A shear stable, multiviscosity grade lubricating oil compositioncomprising mineral oil, and as a viscosity improver a minor amount of analpha-olefin polymer produced from one alpha-olefin monomer having fromfive to 12 carbon atoms or produced from a mixture of alpha-olefinmonomers having from three to 12 carbon atoms with monomers having fromfive to 12 carbon atoms comprising at least about 20 mol percent of themixture and with substantially all of the alternate carbon atoms in eachlinear polymer chain having dependent therefrom the same alkyl grouphaving from three to ten carbon atoms when said linear alpha-olefinpolymer is produced from one alpha-olefin monomer or randomly differentalkyl groups having from one to carbon atoms when said linearalpha-olefin polymer is produced from said mixture of alpha-olefinmonomers.

said alpha-olefin polymer characterized by a weight average molecularweight M between about 50,000 (M/84) and about 1,000,000 (M/84), anumber average molecular weight M, between about 4,000 (M/ 84) and about1,000,000 (M/84) where M is the molecular weight of the alpha-olefinmonomer or average molecular weight of the mixture of alphaolefinmonomers.

a distribution factor M /M of between one and about 12, the upper limitof said distribution factor being about 12 when M is about 50,000 (M/84)and about two when M is about 1,000,000 (M/84) with the upper limit ofsaid distribution factor proportionately decreasing from about 12 toabout two as M increases from about 50,000 (M/84) to about 1,000,- 000(M/84), and

said lubricating oil composition comprising from about 0.5 (M/84) weightpercent to about 10 (M/84) percent of said alpha-olefin polymer in anamount sufficient to provide a multiviscosity grade difference of atleast three in SAE viscosity classification J 300a.

2. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 1 in which said alpha-olefin polymer ischaracterized by a weight average molecular weight M betwen about100,000 (M/84) and about 1,000,000 (M/84), a number average molecularweight M between about 12,000 (M/84) and about 1,000,000 (M/84), and adistribution factor M /M of between one and about nine, the upper limitof said distribution factor being about nine when M is about 100,000(M/84) and about two when M is about 1,000,000 (M/84) with the upperlimit of said distribution factor proportionately decreasing from aboutnine to about two as M increases from about 100,000 (M/84) to about1,000,000 (M/84), and said alpha-olefin polymer present in an amountsufiicient to provide a multiviscosity grade difference of at least fourin accordance with SAE viscosity classification J 300a.

3. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 1 in which said alpha-olefin polymer ischaracterized by a weight average molecular Weight M between about150,000 (M/84) and about 1,000,000 (M/84), a number average molecularweight M between about 35,000 (M/84) and about 1,000,000 (M/84), and adistribution factor M /M of between one and about six, the upper limitof said distribution factor being about six when M is about 150,000(M/84) and about two when M is about 1,000,000 (M/84) with the upperlimit of said distribution factor proportionately decreasing from aboutsix to about two as M increases from about 150,000 (M/84) to about1,000,000 (M/84), and said alpha-olefin polymer present in an amountsufiicient to provide a multiviscosity grade difference of at least fivein accordance with SAE viscosity classification J300a.

4. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 1 in which said 14 alpha-olefin polymer ischaracterized by a weight average molecular weight M between about200,000 (M/84) and about 1,000,000 (M/84), a number average molecularweight M between about 90,000 (M/84) and about 1,000,000 (M/84), and adistribution factor M /M of between one and about three, the upper limitof said distribution factor being about three when M is about 200,000(M/84) and about 1.5 when M is about 1,000,- 000 (M/84) with the upperlimit of said distribution factor proportionately decreasing from aboutthree to about 1.5 as M increases from about 200,000 (M/84) to about1,000,000 (M/84), and said alpha-olefin present in an amount sufiicientto provide a multiviscosity grade difference of at least six inaccordance with SAE viscosity classification J 300a.

5. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 1 in which each alternate carbon atom of thealpha-olefin polymer has dependent therefrom an alkyl group having fromtwo to eight carbon atoms.

6. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 5 in which said lubricating oil compositioncomprises from about 1.0 (M/84) percent to about 6.0 (M/84) percent ofsaid alpha-olefin polymer.

7. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 1 in which the said linear alpha-olefin polymerhas a substantially isotactic structure.

8. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 1 in which each alternate carbon atom of thealpha-olefin polymer has dependent therefrom an alkyl group having fourcarbon atoms.

9. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 8 in which said lubricating oil compositioncomprises from about 1.0 percent to about 3.5 percent of saidalpha-olefin polymer.

10. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 9 in which the said linear alpha-olefin polymerhas a substantially isotactic structure.

11. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 2 in which each alternate carbon atom of thealpha-olefin polymer has dependent therefrom an alkyl group having fromtwo to eight carbon atoms.

12. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 11 in which said lubricating oil compositioncomprises from about 1.0 (M/84) percent to about 6.0 (M/84) percent ofsaid alpha-olefin polymer.

13. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 12 in which each alternate carbon atom of thealpha-olefin polymer has dependent therefrom an alkyl group having fourcarbon atoms.

14. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 13 in which said lubricating oil compositioncomprises from about 1.0 percent to about 3.5 percent of saidalpha-olefin polymer.

15. A shear stable, multiviscosity grade lubricating oil composition inaccordance with claim 14 in which the said linear alpha-olefin polymerhas a substantially isotactic structure.

16. A shear stable, multiviscosity grade lubricating oil in accordancewith claim 3 in which each alternate carbon atom of the alpha-olefinpolymer has dependent therefrom an alkyl group having from two to eightcarbon atoms.

17. A shear stable, multiviscosity grade lubricating oil in accordancewith claim 16 in which each alternate carbon atom of the alpha-olefinpolymer has dependent therefrom an alkyl group having four carbon atoms.

18. A shear stable, multiviscosity grade lubricating oil FOREIGN PATENTSin accordance with claim 17 in which said lubricating oil 676 516 7/1952Great Britain composition comprises from about 1.0 percent to about846685 8/1960 Great Britain n 252 59 3.5 percent of said alpha-olefinpolymer.

References Cited 5 PATRICK P. GAlKVIN, Primary Examiner UNITED STATESPATENTS A. H. METZ, Asslstant Examiner 2,525,788 10/1950 Fontana et a1252-59 US. Cl. X.R.

3,637,503 1/ 1972 Giannetti et a1. 25259 260-882 F

